1. Field of the Invention
The present invention relates to an ATM (Asynchronous Transfer Mode) network and particularly to a technique for converting data of a frame format into a cell which is a transfer format in the ATM network and outputting the cell.
2. Description of Related Art
In order to perform line accommodation of synchronous transfer mode, exchange control, signaling processing, upper layer processing and so on, an ATM cell conversion circuit for converting data of a frame format into a cell format has been used in an ATM exchange since the past. However, processing of ATM cell conversion by this ATM cell conversion circuit often becomes bottleneck of processing of the exchange, so that speedup and high efficiency of processing have been desired.
As the conventional art associated with the ATM cell conversion circuit, the art applicable to an exchange switch for outputting ATM cells to multiple routes or an apparatus of the input side of a multiplexer for multiplexing cells every route is disclosed in Japanese Patent No. 2760343. This ATM cell conversion circuit constructs frame information designated by a processor into ATM cells used in an ATM network with reference to external memory, and outputs the ATM cells to switch means for performing distribution on a output route basis.
In the conventional ATM cell conversion circuit, however, the buffer amount or the ATM network band which the ATM exchange has is finite and on the contrary, consideration of efficiently using finite resources which the exchange or the network has is not given and as the contents of the consideration, for example, a quality class every respective frame or priority assigned every output connection is considered to perform sending.